There is known a plasma processing apparatus that is provided with a processing container, an upper electrode provided within the processing container, and a lower electrode provided within the processing container and connected to a high frequency power supply. In such a plasma processing apparatus, a semiconductor wafer is mounted on the lower electrode, a processing gas is supplied into the processing container, and a high frequency power is applied to the lower electrode. Then, the processing gas within the processing container is turned into plasma by the high frequency power supplied into the processing container through the lower electrode so that, for example, ions, are generated, and a plasma processing such as, for example, an etching processing, is performed on the semiconductor wafer by, for example, the ions.
In the plasma processing apparatus, a reaction product produced from the processing gas containing a reaction gas is adhered to, for example, a side wall of the processing container or the upper electrode. When the reaction product attached to the side wall or the upper electrode is peeled off from the side wall or the upper electrode to form particles and the particles float within the processing container, some of the particles may be attached to the semiconductor wafer. The particles may cause a defect on, for example, a semiconductor device manufactured from the semiconductor wafer. Accordingly, it is necessary to remove the reaction product adhered within the processing container.
For example, there is known a cleaning method in which a negative direct current voltage is applied to the upper electrode and oxygen gas is introduced into the processing container so that oxygen ions and oxygen radicals are generated from the oxygen gas by the high frequency power applied to the lower electrode to cause the reaction product adhered to the upper electrode to react with either the oxygen ions or the oxygen radicals to be removed from the upper electrode.